Method of making three-phase transformer cores



(5. A. SMITH METHOD OF MAKING THREE--PHASE TRANSFORMER CORES Original Filed Dec. 13, 1954 INVENTOR GEOIIG! A. SMITH nited States Patent METHOD OF MAKING THREE-PHASE TRANSFORMER 'CORES George A. Smith, Pine Bluff, Ark, assignor to Central Transformer Corporation, Pine Bluff, Ark., a corporation of Arkansas Original application Dec. 13, 1954, Ser. No. 474,645. Divided and this application Oct. 20, 1955, Ser. No. 541,805

2 Claims. (Cl. 29-15557) This invention relates to certain new and useful improvements in cores for transformers, and particularly relates to such cores formed from magnetic strip material processed to produce a three-phase transformer core, and more particularly relates to a three-phase T-core for transformers. I

This application is a division of my copending application Serial No. 474,645, filed December 13, 1954.

Specifically this invention relates to a new and novel three-phase core for transformers comprising three winding legs in parallel relation, interconnected by substantially T-shaped yoke portions in which one of the three legs has a cross sectional dimension equal to substantially twice the cross sectional dimension of each of the other two legs, and this invention further relates to the new and novel method by which such core is produced.

In order to provide for conditions in which the flux flow qualities of one of the winding legs of a transformer, as in a three phase transformer, may be enhanced, it has become apparent that it is desirable to substantially increase the mass of magnetic material incorporated in one such leg and thereby to enhance the desirable magnetic flow qualities resulting therefrom in a transformer construction.

It has heretofore been contemplated that three-phase cores for transformers may be fabricated employing substantially T-shaped yokes. It has, however, been considered undesirable to attempt to increase the mass of material in any of the winding legs of such construction because of the bulkiness of the resultant product.

The present invention is particularly directed to the production and formation of such T-cores for transformers in which one of the legs is of substantially twice the cross sectional area of the other two legs and is so related to the remaining two legs as to minimize the heretofore undesirable bulkiness.

The principal object of the present invention is to provide a new and novel method of fabricating a three-phase core for transformers.

A further object of the invention is to provide a method of fabricating a three-phase core for transformers which includes the steps of associating with a substantially continuous coil of magnetic strip material, a bundle of U-shapedlaminations, interleaving alternate said U-shaped layers with turns of said coil, and butting the interposed U-shaped laminations against edge portions of the coil.

A further object of the invention is to provide a new and novel method of fabricating three-phase cores for transformers which comprises forming a three-phase core having T-shaped yoke portions, in which one of the winding legs is of a cross sectional area equal to substantially twice the cross sectional area of the remaining legs.

A further object of the invention is to generally improve the efiiciency and facility in methods of fabricating three-phase cores for transformers.

The means by which the foregoing and other objects of the present invention are accomplishedand the manner of their accomplishment will readily be understood from the following specification upon reference to the accompanying drawings, in which:

Fig. 1 is a face view of a substantially rectangular continuous coil of magnetic strip material as employed in the present invention.

Fig. 2 is a face view of a coil similar to the coil of Fig. 1, in which the short sides of the coil have been served along a line parallel to an offset from the longitudinal center line of the coil to produce two U-shaped bundles of lamination layers.

Fig. 3 is a face view of a composite U-shaped bundle of lamination layers formed from the two bundles of Fig. 2.

Fig. 4 is a perspective view of a transformer core formed in accordance with the present invention; and

Fig. 5 is a fragmentary sectional view through one of the yoke portions of the core of Fig. 4, as on the line Referring now to the drawings in which the various parts are indicated by numerals, the present invention relates to a new and novel method of fabricating threephase cores for transformers and to the new and novel core produced thereby.

In the preferred practice of the invention magnetic strip material is withdrawn from a suitable source of supply, not shown, and is introduced to a suitable winding mechanism, preferably in the form of a substantially rectangular mandrel 11, which is preferably rotatably supported as by a shaft 12. Rotation of the mandrel, with the magnetic strip material engaged therewith, is undertaken to bend the strip material flatwise and produce a substantially rectangular coil 13 of a plurality of lamination layers. During the formation of coil 13 suitable spacers 15 are interposed between the successive layers along the short sides thereof providing upon completion of formation of the coil spaces between adjacent layers.

The rectangular coil 13 thus produced includes a pair of winding leg portions 17, 18 formed by the long sides of the coil and connecting yoke portions 20, 21 formed by the short sides of the coil. Preferably a second coil, like the coil 13 and having an equivalent number of whole turns and lamination layers, is formed upon a mandrel 11 and is severed, as best shown in Fig. 2, as at 23, 24, along a line parallel to but laterally offset from the longitudinal center line of the coil to divide second coil 13 into a substantially U-shaped bundle 25 of major lamination layers 26 and a minor U-shaped bundle 27 of minor lamination layers 28. The major lamination layers 26 each includes a winding leg portion 26A and opposite yoke portions 26B, 26C, bent substantially at right angles to the leg portions 26A. Minor lamination layers 28 include winding leg portions 28A and opposite yoke portions 28B, 28C. The yoke portions 26B, 26C exceed the length of the yoke portions 28B, 280 by an amount of the nature of the width of the strip material from which the coils and lamination layers are formed.

The respective lamination layers 26, 28 of the bundles 25, 27 are unstacked and are alternately nested together to form a composite U-shaped bundle 31, best shown in Fig. 3. Bundle 31 comprises a winding leg 32 composed of the alternate winding leg portions 26A, 28A and comprises a plurality of lamination layers substantially equal in number to twice the number of lamination layers comprising the layers of which the winding legs 17, 18 are formed. At its opposite ends the composite bundle 31 includes yoke portions 33, 34 respectively composed of yoke portions 26B, 28B and 26C, 28C. Like the winding leg 32, the yoke portions 33, 34 are each composed of a plurality of layers substantially equal in number to twice the layers comprising the yoke portions 20, 21, and in addition each of the yoke portions 33, 34 includes projecting portions formed of the end sections of the yoke portions 26B, 26C, substantially equal in number to the layers comprising the yoke portions 20, 21.

In the assembly of the core of the present invention, a coil 13 is formed as described and preferably threaded through the windows of phase windings 35, the spacers 15 being preferably removed during the association of the coil 13 with phase windings 35. The composite bundle 31 is formed up as described and the successive lamination layers 26, 28, of which bundle 31 is formed, are laced through the window of a third phase winding 37, positioning the winding leg 32 within phase winding 37 with composite yoke portions 33, 34 projecting substantially at right angles at the opposite ends of winding leg 32.

The extending end portions of yoke portions 26B, 26C are then successively interleaved into spaces between the lamination layers of the yoke portions 29, 21 of coil 13 and the assembled devices may be bound together with suitable binders 39.

It will be observed that the end portions of yoke portions 26B, 26C fully overlap the width of the layers comprising yoke portions 20, 21 and that the square ends of yoke portions 28B, 28C are respectively abutted against the edges of the layers in yoke portions 20, 21.

It will be seen that the cross sectional area of winding leg 32 is substantially twice the cross sectional area of winding legs 17 and 18 and that the winding legs are interconnected in substantially parallel relation by substantially T-shaped yoke portions.

It further will be observed by virtue of the present constructions that the joints between the coil yoke portions 20, 21 and bundle yoke portions 33, 34 are maintained without excessive bulkiness and do not exceed in cross sectional dimension the cross sectional area of major winding leg 32. By virtue of the full lap joints between yoke portions 26B, 26C, and coil yoke portions 20, 21 supplemented by the butt joints between yoke portions 28B, 28C and the edges of coil yoke portions 20, 21, a superior jointing arrangement is produced, greatly enhancing the magnetic flow qualities of the transformer core thus produced and enabling the prodnction of the T-core in which one of the legs is of substantially increased cross sectional area relative to the two remaining three legs.

The term lamination layer has been used herein since there may be more than one lamination in each layer.

I claim:

1. A method of fabricating three-phase cores for transformers comprising the steps of forming a substantially quadrilateral first coil comprising a plurality of continuously interconnected lamination layers of relatively narrow magnetic strip material having parallel sides and parallel legs, successively spacing apart said layers along said sides substantially the thickness of a single layer during coil formation, similarly forming from said material a second said coil of a like plurality of layers having substantially parallel legs and substantially parallel sides, severing the sides of said second coil layers along a line parallel to and offset from the center line of said second coil a distance equal to substantially one-half the width of said narrow material to produce a like plurality of substantially U-shaped major lamination layers, and a plurality of substantially U-shaped minor lamination layers, alternately interleaving said minor lamination layers with said major lamination layers in nested relation to create a substantially U-shaped bundle of a multiplicity of lamination layers substantially equal in number to twice the plurality of layers in said first coil with end portions of said major U-shaped laminations projecting beyond the ends of said minor laminations a distance substantially equal to the width of said material, successively inserting said projecting end portions in the spaces between said first coil layers to overlie the width thereof and abutting the ends of said interleaved minor laminations against edge portions of said first coil layers adjacent said spaces to join said bundle to opposite sides of said coil, whereby to fabricate a core structure having three winding legs in substantially parallel relation in which said bundle provides a winding leg having a cross sectional area equal to substantially twice the cross sectional area of each of the other legs and the junction between said coil and said bundle is substantially T-shaped and of a thickness substantially equal to the thickness of said bundle winding leg.

2. A method of fabricating three-phase cores for transformers comprising the steps of forming a substantially quadrilateral first coil comprising a plurality of continuously interconnected lamination layers of relatively narrow magnetic strip material including substantially parallel sides and parallel legs, successively spacing apart said layers along said sides substantially the thickness of a single layer during coil formation, similarly forming from said material a second said coil of a plurality of layers having substantially parallel legs and substantially parallel sides, severing the sides of said second coil layers along a line parallel to and offset from the center line of said second coil to produce a plurality of substantially U-shaped major lamination layers, and a plurality of substantially U-shaped minor lamination layers, alternately interleaving said minor lamination layers with said major lamination layers in nested relation to create a substantially U-shaped bundle of a multiplicity of lamination layers with end portions of said major U-shaped laminations projecting beyond the ends of said minor laminations, successively inserting said projecting end portions in the spaces between said first coil layers in overlying relation to said first core layers and abutting the ends of said interleaved minor laminations against edge portions of said first coil layers adjacent said spaces to join said bundle to opposite sides of said coil, whereby to fabricate a core structure having three winding legs in substantially parallel relation in which the junction between said coil and said bundle is substantially T-shaped.

References Cited in the file of this patent UNITED STATES PATENTS 1,102,513 .Tohannesen July 7, 1914 1,935,426 Acly Nov. 14, 1933 2,483,159 Somerville Sept. 27, 1949 2,516,164 Vienneau July 25, 1950 

